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  1. #1
    Senior Member paul2010's Avatar
    Join Date
    Jan 2010

    Low/High clew wave sails

    what are the pros/cons between those two design standards?

  2. #2
    When you change between a high and a low clew design, you very clearly notice it as it affects your stance, but I think you get used to that fairly quickly. It might be something to consider when planning a quiver though.

    On a more technical side, the obvious aspect has to do with some bard bottom turn situations where the clew might hit the water. This a much bigger issue on bigger sails, say 5.3 and up and below 4.7 it's normally not an issue even on low clew designs. Clew height will also influence things when doing some tricks, particularly when you go pass the clew in front of you.

    Beyond that is get quite involved. The clew heigh will influence the tension in the sail and how the boom "connects" to the sail. Lower clew leaves the leech looser and may also give the whole boom a less direct connection to the sail in transitions. Another aspect that influences this is how close the batten ends are to the boom connection as well as the outhaul tension needed to set the sail (and those two aspects are in themselves interconnected). But at this technical level it get less interesting to look at the clew height as an isolated feature. There are so many variables that interrelate so it is simply better to two to get a feel for the feel of the sail as a whole.
    Ola H.

    Simmer Style Boards and Sails

  3. #3
    Isn't clew height just the same as boom height for most stance issues?
    Having a higher clew simply means a different angle of the boom on the mast for the same boom height at your harness lines and where you hold on.

    In the old days people would tell you that different boom angles would change relative foot and leech tensions – but that's actually rubbish with a modern sail. Ola's description is the opposite to how most would describe that.

    Some sails have two clew cringles mostly to give taller sailors the chance of getting their boom higher.
    But the difference is only a few centimetres.
    It's a very useful option however for those already needing to set the boom at the top of the cutaway at the front end – the higher clew then keeps the boom angle more horizontal.
    Last edited by basher; 1st August 2011 at 08:46 AM.
    Now back in the UK.

  4. #4
    Quote Originally Posted by basher View Post
    In the old days people would tell you that different boom angles would change relative foot and leech tensions but that's actually rubbish with a modern sail. Ola's description is the opposite to how most would describe that.

    I agree that the angle will not by itself matter in a typical wave sail and many other factors will influence leech action a lot too. But (as most easily noted on extremely small sails where changes relatively speaking have a bigger effect on geometry) with a lower clew, there is simply more leech that can work independently from the boom. Ie, it's not the angle, but the actual position where "you" (via the boom) connect the the rear part of the sail. Imagine the clew one meter further up the sail than normal. It would be kind of hard to get a decent twisting sail... Well, with a 3.0 sail and the clew in a normal position relative the ground you're getting closer to that scenario. And by extrapolation, there will be such effects also on normal sized sails.

    I once got a 3.5 sail from Hot that probably was never tested and just downscaled from bigger sizes. And maybe the designer was a bit tired that day... so the sail was scaled down in a way so that the clew got super low. The boom angle created took some getting used to and the sail was EXTREMELY sensitive to outhaul trim (and trim in general). There was very little between the sail just getting totally flat and a state where it felt like the boom was not attached to the clew at all. But when you got it right, this was in fact one of the best feeling 3.5 sails I've used when it comes to how active and "normal" it felt.
    Ola H.

    Simmer Style Boards and Sails

  5. #5
    Sail twist is mostly a function of mast bend and luff round. Sail twist at the head is also a function of roach.

    If we cared a lot about clew height we'd make it higher as the sails got bigger.

    I'm not sure anyone will notice the different handling characteristics of a higher clew sail – the way the sail works on the mast chosen will still be the main issue.

    A higher clew may help or hinder duck moves – but even there that's more an issue of how much 'foot round' the sail has.
    Last edited by basher; 1st August 2011 at 09:34 AM.
    Now back in the UK.

  6. #6
    Senior Member Sailrepair's Avatar
    Join Date
    Feb 2010
    basher - I remember a few years ago you telling me I was talking rubish when I suggested that you could alter leech tensions by choosing which eylet to use (given a choice). Now you have people like goya sails saying the same, its even printed on their sails. You also have the likes of Pryde saying they have droped their clews to free up the leech more.

    Personaly I like my boom angle to be the same on all my sails you can see all my clew positions here marked out

    Sorry about photo size, I'll resize it when I get time.edit - done

    If I use a North & naish sail I find their clews too low but I'd probably get used to it. The argument of using clew hight to alter the leech tension - it does but I'd rather do that with luff curve. I like quite high clews, being 6'2" might have something to do with that. When I occasionaly lend some one small one of my rigs, they have to put the boom down. I expect them to say the clew is too high but they never do.
    Last edited by Sailrepair; 1st August 2011 at 10:15 AM.

  7. #7

    Late edit; Thanks for changing pic size.
    Last edited by basher; 3rd August 2011 at 10:02 PM.
    Now back in the UK.

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